I can't get Gmail to swipe left on my phone to trash even though I went to Advanced settings > Advanced for Gmail and the deleted mailbox is checked. Why is Gmail still showing only the archive as an option when swiping left? I have iPhone 6 with iOS 10.1.
Go into Settings > Mail, and tap on your Gmail account. Then tap account again, then Advanced. Look for "Move Discarded Messages Into" section and tap Deleted Mailbox.